Detonation from stock GT under WOT

[Mustang5L5]

I have been expeirencing detonation under load with my '03 GT which is stock aside from K&N, cat-back and shifter.

It usually comes on at WOT in 3rd gear, but i have sometimes gotten it in 2nd gear.

I run 87 octane from Mobil, but go to different stations. Car has 25K miles on it.

I don't want to bring it to Ford just yet and let them beat on my car on the highway trying to duplicate it.

Has anyone else expeirenced this? It usually happens in the upper RPM's and i can hear it with the window down especially if i'm next to a wall or another car.

 

[Black2001GT]

I did in my 01 GT. I only use Midgrade or High octane.

 

[hotmustang331]

My car SOUNDS like it is detinating when next to a wall, and ONLY at WOT @4500+ RPMs and seems to be in every gear. But its the exhaust...for some reason is supper raspy. You cant hear it W/ windows up, only when down and gets SUPER loud when next to another vehicle at WOT....sounds crappy. Maybe thats what yours is doing?

But easiest thing to do is fillup with 93 and see what happenes. My exhaust does it regaurdless of timing or octain.

 

[ponysarepretty]

Clean the MAF?

 

[ADRENLN]

yea somthin on my car has been sounding crappy for a while espesially next to a wall. dont know what it is, but it happens driving in every gear and i dont have to be at wot as long as im passing cars or next to a wall. i dont think its detonation, but who knows.

i just think thhese cars sound like ****. try 93 and see if it helps, it dont make any difference with mine.

o/t can you send me a bigger pic of the hot chick in your aveator?

 

[Mustang5L5]

it could be the exhaust. My exhaust is stock except for a cat-back flowmaster setup, but i do know i have a tiny leak where the tailpipes bolt up. Been meaning to fix it but have had no time all summer to crawl under the car.

I guess with 25K i should address some minor tune up issues anyway. Clean the MAF out. Some oil from the K&N could have built up there so i should check that out. If that is the case i'll just go back to a stock filter and ebay the K&N. This is my daily driver so HP isn't as important as running 100%.

I guess now is a good time to do plugs too. Should i stay with the factory platnium replacements or switch to coppers?

 

[tomustang]

higher octane

 

[White Stang]

Pull a spark plug and see if you can see any dark specs on the porclien. If you do then it is detonation if not it is most likely someting else.

 

[bdcardinal]

you might have some carbon buildup on the pistons. try using some seafoam. check the plugs and see how they look. also change the fuel filter.

 

[40th GT]

Yes, definitely try the Seafoam and I'd do it all three ways. Your TB is most likely caked with carbon too. On my car, with 89 octane it feels like I'm pulling a trailer but she runs like bat outta hell with 87. I'm on the stock tune and if you are too, then do whatever you can to try and run 87 w/o pinging.

 

[sgarlic]

I'd take it to Ford, and tell the service manager you're going along for the test drive.